CA1078582A - Potassium phosphate fertilisers - Google Patents
Potassium phosphate fertilisersInfo
- Publication number
- CA1078582A CA1078582A CA206,056A CA206056A CA1078582A CA 1078582 A CA1078582 A CA 1078582A CA 206056 A CA206056 A CA 206056A CA 1078582 A CA1078582 A CA 1078582A
- Authority
- CA
- Canada
- Prior art keywords
- product
- potassium
- reaction
- content
- phosphoric acid
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Fertilizers (AREA)
Abstract
POTASSIUM PHOSPHATE FERTILISERS
Abstract of the Disclosure The invention is an improvement to the process for producing potassium phosphate or polyphosphate in which potassium chloride and phosphoric acid or a polyphosphoric acid are reacted together in a molar ratio of phosphorus to potassium in the range of 1:1 to 1.25:1. The novel feature comprises the removal of hydrochloric acid from the reaction mass by sparging the reaction mass with air to remove chloride.
Abstract of the Disclosure The invention is an improvement to the process for producing potassium phosphate or polyphosphate in which potassium chloride and phosphoric acid or a polyphosphoric acid are reacted together in a molar ratio of phosphorus to potassium in the range of 1:1 to 1.25:1. The novel feature comprises the removal of hydrochloric acid from the reaction mass by sparging the reaction mass with air to remove chloride.
Description
'7~
This invention relates to the prod~lction of ~erki-lisers and is particularly concerned with the production o~
potassium dihydrogen phosphate and/or soluble polym~rised forms of this sal~. These materials are of great value as sources of both potassium and phosphor~us and can be used as fertilisers directly o~ together with other components.
Potassium dihydrogen phosphate can be obtained by the reaction of phosphoric acid with potassium chloride according to the well-known reaction:
KCl + H3PO4 ~ KH2PO4 + HCl The removal of the hydrogen chloride quantitatively from the reaction mass is extremely difficult in practice, unless high temperatures or a large excess of phosphoric acid are used. In the former case, the water-insoluble potas-sium metaphosphate is preferentially formed and, in the latter case, the isolation of the s~lt from the acid is difficult and expensive in practice.
According to our invention we provide a process for the production of potassium phosphate or polyphosphate in which potassium chloride and phosphoric acid or a poly-phosphoric acid are reacted together in a molar ratio of 1.25:1 inclusive and the entire reaction being at a temperature in the range of 220 C. to 250~C" air being blown through the reaction mixture to facilitate the removal of hydrochloric acid and either cooling the reaction product to form a glass-like solid with a' chloride content of less than 1.5% and a free acid content of less than.l5% P205 or hydrol.~sing the reaction product by heating with water an~ recovering the hydrolysis product as a crystalli.ne solid.
This invention relates to the prod~lction of ~erki-lisers and is particularly concerned with the production o~
potassium dihydrogen phosphate and/or soluble polym~rised forms of this sal~. These materials are of great value as sources of both potassium and phosphor~us and can be used as fertilisers directly o~ together with other components.
Potassium dihydrogen phosphate can be obtained by the reaction of phosphoric acid with potassium chloride according to the well-known reaction:
KCl + H3PO4 ~ KH2PO4 + HCl The removal of the hydrogen chloride quantitatively from the reaction mass is extremely difficult in practice, unless high temperatures or a large excess of phosphoric acid are used. In the former case, the water-insoluble potas-sium metaphosphate is preferentially formed and, in the latter case, the isolation of the s~lt from the acid is difficult and expensive in practice.
According to our invention we provide a process for the production of potassium phosphate or polyphosphate in which potassium chloride and phosphoric acid or a poly-phosphoric acid are reacted together in a molar ratio of 1.25:1 inclusive and the entire reaction being at a temperature in the range of 220 C. to 250~C" air being blown through the reaction mixture to facilitate the removal of hydrochloric acid and either cooling the reaction product to form a glass-like solid with a' chloride content of less than 1.5% and a free acid content of less than.l5% P205 or hydrol.~sing the reaction product by heating with water an~ recovering the hydrolysis product as a crystalli.ne solid.
- 2 -s&~
The preferre~ n,~lar ratio of pho~phoru~ to potas3ium i~ sub~tantially l.l:l.
The resulting reaction product is itself a valuable fertiliser product which may be used without further treat-ment. Alternatively, the reaction product may be hydrolysed by heating with water at temperatures in the neighbourhood of 100 C., e.g. 100-120 C the product of hydrolysis being thereafter recovered. The reaction product when cooled is a glass-like solid which dissolves in water to give ~olutions of high analysis which can be used for the production of liquid fertili~ers. The hydrolysis product can be recovered as a crystalline solid and can likewise be dissolved in water for the produckion of liquid fertilizers.
The phosphoric acid employed in this reaction is normally commercial phosphoric acid containing from 50 to 54~ P2O5. We may, however, use instead as the phosphoric acid reactant dehydrated commercial phosphoric acid con-taining more than 54% and less than 75% of P205.
;) In general, phosphoric acid with a P205 content in the range of from 30% to 75% may be used.
Liquid fertilisers with a very low chloride content may be manufactured by dissolving the hydrolysed product in water or alternatively in an ammonia solution or by forming a solution of the reaction product of the hydro-lysis product in water and khereafter passing gaseous ammonia through the solution.
The process of the invention involves the production of pota3sium dihydrogen pho3phate and polymer3 of this ~0 salt by the reaction of phosphoric acid with pota3sium chloride accordlng to the well-known reaction:
D
: . .
`-`` 10~8582 KCl + H3PO4 -~ KH2PO4 + HCl Dehydration of the orthophosphate takes place at the elevated temperature to yield pyrophosphate and higher polymeric phosphates. The temperature of reaction (220-250C) is sufficiently low however, to avoid the formation of insoluble metaphosphate.
We have found in accordance with our invention that the removal of chloride from the reaction mass can be easily and effectively carried out with stoichiometric or near stoichiometric quantities of reagents, the P to K mol ratio varying from 1.0 : 1 to 1.25:1 without the use of very high temperatures or large excesses of acid, by sparging the reaction mass with air.
The process of the invention has the advantage o avoiding the preferential formation of water insoluble metaphosphate and also the difficult and expensive isolation of the desired potassium dihydrogen phosphate salt from large excesses of accompanying acid.
2~
~., ' .
.
~785~Z
The phosphoric acid employed may be the we-t process phosphoric acid of commerce with potassium pentoxide content in the range of from 30 to 54% or it may be dehydr~ted phosphoric acid with a P205 content of substantially 75~, or the superphosphoric acid of commerce or various other grades of phosphoric acid which are commercially available.
The resulting glass-like product is a polymerised mixture of phosphates with a small amount of free acid present varying from 5% to 15~ P205 depending on the relative quantities o~ acid and potassium chloride used, which can be ground up to yield fertiliser material of high P205 and K20 analyses or dissolved in water to yield a liquid fertiliser of high analysis and low chloride content.
The mass is hydrolysed by heating with water at temperatures of substantially the boiling point of water so as to yield the solid potassium dihydrogen phosphate product. This product can be dried to yield a friable -powder or dissolved in water to yield a liquid fertiliser of high analysis containing potassium and phosphate with ~-a very low chloride content.
According to one embodiment of the process according to the invention, the reaction product is recovered as a glass-like solid with a chloride content of less than 1.5 and a free acid content of less than 15~ P205.
Factors whic~ affect the chloride content of the product are the reaction temperature and the ratlo of phosphoric acid to potash. Other reaction conditions which influence the chloride content are the reaction time and 1C~';'8~i~Z
the air sparging of the reaction mass as illustrated in the following Examples 3 and 2 respectively. Thus in the following Example 1, a product having a chloride content of below 1.5~ could be obtained if the mole ratio of P to K was raised above 1.1, or if the temperature was raised above 250C, or if the residence time was increased.
The solution of either the reaction or hydrolysis product can be ammoniated to give a stable solution with analyses for N, P and K which are much higher than it has been possible to achieve up to now with commercial materials.
We have found that although high analysis solutions can be obtained with the hydrolysed product, whiah is an orthophosphate, solutions having even higher - .
~ . .
.. ..
- ~0'785~
analyses can be obtained by dissolving the polytler~c reaction product in water. The reaction ~roduct is therefore a u~eul material for the production of llquid fertilisers. For those purposes in which handling and transport of the product is necessary or in which a solid product is required the hydrolysed product is advantageously used.
An apparatus which may be used ~or carrying out the process according to the invention is described with reference ~ to the accompanying flow-sheet of a process for making potassium phosphate from muriate of potash.
The apparatus shown in the drawing comprlses a reactor
The preferre~ n,~lar ratio of pho~phoru~ to potas3ium i~ sub~tantially l.l:l.
The resulting reaction product is itself a valuable fertiliser product which may be used without further treat-ment. Alternatively, the reaction product may be hydrolysed by heating with water at temperatures in the neighbourhood of 100 C., e.g. 100-120 C the product of hydrolysis being thereafter recovered. The reaction product when cooled is a glass-like solid which dissolves in water to give ~olutions of high analysis which can be used for the production of liquid fertili~ers. The hydrolysis product can be recovered as a crystalline solid and can likewise be dissolved in water for the produckion of liquid fertilizers.
The phosphoric acid employed in this reaction is normally commercial phosphoric acid containing from 50 to 54~ P2O5. We may, however, use instead as the phosphoric acid reactant dehydrated commercial phosphoric acid con-taining more than 54% and less than 75% of P205.
;) In general, phosphoric acid with a P205 content in the range of from 30% to 75% may be used.
Liquid fertilisers with a very low chloride content may be manufactured by dissolving the hydrolysed product in water or alternatively in an ammonia solution or by forming a solution of the reaction product of the hydro-lysis product in water and khereafter passing gaseous ammonia through the solution.
The process of the invention involves the production of pota3sium dihydrogen pho3phate and polymer3 of this ~0 salt by the reaction of phosphoric acid with pota3sium chloride accordlng to the well-known reaction:
D
: . .
`-`` 10~8582 KCl + H3PO4 -~ KH2PO4 + HCl Dehydration of the orthophosphate takes place at the elevated temperature to yield pyrophosphate and higher polymeric phosphates. The temperature of reaction (220-250C) is sufficiently low however, to avoid the formation of insoluble metaphosphate.
We have found in accordance with our invention that the removal of chloride from the reaction mass can be easily and effectively carried out with stoichiometric or near stoichiometric quantities of reagents, the P to K mol ratio varying from 1.0 : 1 to 1.25:1 without the use of very high temperatures or large excesses of acid, by sparging the reaction mass with air.
The process of the invention has the advantage o avoiding the preferential formation of water insoluble metaphosphate and also the difficult and expensive isolation of the desired potassium dihydrogen phosphate salt from large excesses of accompanying acid.
2~
~., ' .
.
~785~Z
The phosphoric acid employed may be the we-t process phosphoric acid of commerce with potassium pentoxide content in the range of from 30 to 54% or it may be dehydr~ted phosphoric acid with a P205 content of substantially 75~, or the superphosphoric acid of commerce or various other grades of phosphoric acid which are commercially available.
The resulting glass-like product is a polymerised mixture of phosphates with a small amount of free acid present varying from 5% to 15~ P205 depending on the relative quantities o~ acid and potassium chloride used, which can be ground up to yield fertiliser material of high P205 and K20 analyses or dissolved in water to yield a liquid fertiliser of high analysis and low chloride content.
The mass is hydrolysed by heating with water at temperatures of substantially the boiling point of water so as to yield the solid potassium dihydrogen phosphate product. This product can be dried to yield a friable -powder or dissolved in water to yield a liquid fertiliser of high analysis containing potassium and phosphate with ~-a very low chloride content.
According to one embodiment of the process according to the invention, the reaction product is recovered as a glass-like solid with a chloride content of less than 1.5 and a free acid content of less than 15~ P205.
Factors whic~ affect the chloride content of the product are the reaction temperature and the ratlo of phosphoric acid to potash. Other reaction conditions which influence the chloride content are the reaction time and 1C~';'8~i~Z
the air sparging of the reaction mass as illustrated in the following Examples 3 and 2 respectively. Thus in the following Example 1, a product having a chloride content of below 1.5~ could be obtained if the mole ratio of P to K was raised above 1.1, or if the temperature was raised above 250C, or if the residence time was increased.
The solution of either the reaction or hydrolysis product can be ammoniated to give a stable solution with analyses for N, P and K which are much higher than it has been possible to achieve up to now with commercial materials.
We have found that although high analysis solutions can be obtained with the hydrolysed product, whiah is an orthophosphate, solutions having even higher - .
~ . .
.. ..
- ~0'785~
analyses can be obtained by dissolving the polytler~c reaction product in water. The reaction ~roduct is therefore a u~eul material for the production of llquid fertilisers. For those purposes in which handling and transport of the product is necessary or in which a solid product is required the hydrolysed product is advantageously used.
An apparatus which may be used ~or carrying out the process according to the invention is described with reference ~ to the accompanying flow-sheet of a process for making potassium phosphate from muriate of potash.
The apparatus shown in the drawing comprlses a reactor
3 which is fed with phosphoric acid from a storage vessel 1 and muriate of potash from a storage vessel 2. Air is fed in at 12.
Hydrochloric acid together with some water vapour is evolved at `
Hydrochloric acid together with some water vapour is evolved at `
4. The product of the reactor 3 may be ~ed to a hydration apparatus 5 where it is mixed with water from a conduit 6. The hydrated product from the hydration apparatus 5 is fed to a `
drying unit 7 and thence to storage 8.
Alternatively, the product from the reactor 3 may be fed 2Q to a cooler 9 and thence to a crusher 10 from which is passed to storage 11.
According to another modification, the product from reactor 3 goes to a second reactor where it is again treated with air. The product from the second reactor then continues on the same paths described above.
': . ' , 3S8~
EX~PLE 1 Fertiliser yrade potassium chloride (Muriate of Potash 60~ K20) was fed at a constant rate 11800 g/hr) with phosphoric acid to an air sparyed reactor maintained at 250C. The ratio o~ phosphoric acid to potash in the feeds was suc'n as to give a reactor product containing 1.10 ~oles P per mole K. The reactor was sparged with air at the rate of 15 litres/minute, The product from this reactor was allowed to flow con-tinuously to a second reactor where the temperature was 250 C. and the air sparging rate was again 15 litres/min. The resulting product was analysed at intervals and contained an average free acid content, expressed as P205 of 7.7% and an average chloride content of 1.5%. The average analysis was:
54.5% total P205 32.6~ total K20 48.5% sol. P205 29.4% sol. K20 The reactor product was divided into two streams, one of which was chilled, crushed and bagged. The other stream was heated with water at 110C. for 2i hours to hydrolyse the phosphates and the hydrolysed product was cooled, vacuum dried and stored. The hydrolysed product had an analysis of 49.2% total P20~, 29.4% total K20.
The glass like reactor product and the hydrolysed product were dissolved in water and saturated solu-tions at 20C. obtained. The saturated solutions had potassium analyses given below:
Reactor product solution (~K20) 1~.5 Hydrolysed product solution (%IC20) 7.9 ,~
. i : - .
)78SBZ
EX~PLE 2 Fertiliser yrade potassium chloride (Muriate of Potash 60% K20) ~00 g was reacted at 220C. wi-th stirring with wet process phosphoric acid (~S2 g) which had been heated to 250C. and concentrated to 58.8% P205. This corresponds to a mole ratio of P to K of 1.4 to 1Ø
When the evolution of hydrochloric acid ilad ceased the reaction mass was divided into two p~rts and each part heated at 220C. for 120 mlnutes. One portion was sparged with air through a glass tube. The other portion was unsparged. The reaction mass was analysed as follows:
Air Sparged Unsparged Residual chloride %Cl 1.64 3.21 Total P205~ 55.6 54.5 Total K20~ 26.4 25.9 EX~'~PLE 3 Fertiliser grade potassium chloride (Muriate of Potash 60% K20)200 g was reacted at 220C. with stirring with wet process phosphoric acid 356 g which had been concentrated to 58.8% P205. This is equal to a mole ratio of P to K of l.l to 1Ø- When the evolution of hydrochloric acid gas had ceased, as indicated by the cessation of effervescence, the mixture was sparged with air and the temperature maintained at 220C. Samples were removed for chloride analysis at intervals. The results of these analyses are yiven below:
Time after cessation of effervescence (mins) 120 1~0 2~0 300 Residual chloride % Cl 6.56 ~.g6 3.5~ 2.6 The analysis of ~he final product was Total P205% 53.1 Total K20~ 31.9 g _ :
:'. ,:, .
The glass-like reaction product and the hydrolysis product thereof may be ammoniated to produce products with valuable K, N, P contents.
Thus, for example, 150 ml of a 20% aqueous ammonia solution was mixed with 203 g of reactor product. The resulting solution containing 4.2~N, 33~ P205 and 17.8% K20 was formulated as a valuable fertiliser.
.
. . . :
.
drying unit 7 and thence to storage 8.
Alternatively, the product from the reactor 3 may be fed 2Q to a cooler 9 and thence to a crusher 10 from which is passed to storage 11.
According to another modification, the product from reactor 3 goes to a second reactor where it is again treated with air. The product from the second reactor then continues on the same paths described above.
': . ' , 3S8~
EX~PLE 1 Fertiliser yrade potassium chloride (Muriate of Potash 60~ K20) was fed at a constant rate 11800 g/hr) with phosphoric acid to an air sparyed reactor maintained at 250C. The ratio o~ phosphoric acid to potash in the feeds was suc'n as to give a reactor product containing 1.10 ~oles P per mole K. The reactor was sparged with air at the rate of 15 litres/minute, The product from this reactor was allowed to flow con-tinuously to a second reactor where the temperature was 250 C. and the air sparging rate was again 15 litres/min. The resulting product was analysed at intervals and contained an average free acid content, expressed as P205 of 7.7% and an average chloride content of 1.5%. The average analysis was:
54.5% total P205 32.6~ total K20 48.5% sol. P205 29.4% sol. K20 The reactor product was divided into two streams, one of which was chilled, crushed and bagged. The other stream was heated with water at 110C. for 2i hours to hydrolyse the phosphates and the hydrolysed product was cooled, vacuum dried and stored. The hydrolysed product had an analysis of 49.2% total P20~, 29.4% total K20.
The glass like reactor product and the hydrolysed product were dissolved in water and saturated solu-tions at 20C. obtained. The saturated solutions had potassium analyses given below:
Reactor product solution (~K20) 1~.5 Hydrolysed product solution (%IC20) 7.9 ,~
. i : - .
)78SBZ
EX~PLE 2 Fertiliser yrade potassium chloride (Muriate of Potash 60% K20) ~00 g was reacted at 220C. wi-th stirring with wet process phosphoric acid (~S2 g) which had been heated to 250C. and concentrated to 58.8% P205. This corresponds to a mole ratio of P to K of 1.4 to 1Ø
When the evolution of hydrochloric acid ilad ceased the reaction mass was divided into two p~rts and each part heated at 220C. for 120 mlnutes. One portion was sparged with air through a glass tube. The other portion was unsparged. The reaction mass was analysed as follows:
Air Sparged Unsparged Residual chloride %Cl 1.64 3.21 Total P205~ 55.6 54.5 Total K20~ 26.4 25.9 EX~'~PLE 3 Fertiliser grade potassium chloride (Muriate of Potash 60% K20)200 g was reacted at 220C. with stirring with wet process phosphoric acid 356 g which had been concentrated to 58.8% P205. This is equal to a mole ratio of P to K of l.l to 1Ø- When the evolution of hydrochloric acid gas had ceased, as indicated by the cessation of effervescence, the mixture was sparged with air and the temperature maintained at 220C. Samples were removed for chloride analysis at intervals. The results of these analyses are yiven below:
Time after cessation of effervescence (mins) 120 1~0 2~0 300 Residual chloride % Cl 6.56 ~.g6 3.5~ 2.6 The analysis of ~he final product was Total P205% 53.1 Total K20~ 31.9 g _ :
:'. ,:, .
The glass-like reaction product and the hydrolysis product thereof may be ammoniated to produce products with valuable K, N, P contents.
Thus, for example, 150 ml of a 20% aqueous ammonia solution was mixed with 203 g of reactor product. The resulting solution containing 4.2~N, 33~ P205 and 17.8% K20 was formulated as a valuable fertiliser.
.
. . . :
.
Claims (9)
1. A process for the production of potassium dihydroyen phosphate or polyphosphate in which potassium chloride and phosphoric acid or a polyphosphoric acid are reacted together in a molar ratio of phosphorus to potassium within the range of from 1:1 to 1.25:1 inclusive with air being blown through the reaction mixture to facilitate the removal of hydrochloric acid and the entire reaction being carried out at a temperature in the range from 220°C to 250°C and either cooling the reaction product to form a glass-like solid with a chloride content of less than 1.5% and a free acid content of less than 15% P2O5 or hydrolysing the reaction product by heating with water and recovering the hydrolysis product as a crystalline solid.
2. A process as claimed in claim 1 in which the mol ratio of phosphorus to potassium is substantially 1.1 : 1.
3. A process as claimed in claim 1 or 2 in which the reaction product is cooled and recovered as a glass-like solid with a chloride content of less than 1.5% and a free acid content of less than 15% P2O5.
4. A process as claimed in claim 1 in which the reaction product is hydrolysed by heating with water and the hydrolysis product is recovered as a crystalline solid.
5. A process as claimed in claim 4 in which the hydrolysis is effected with water at a temperature of from 100 to 120°C.
6. A process according to claim 5 in which the hydrolysis is effected at substantially 110°C.
7. A process as claimed in claim 1 in which phosphoric acid with a P2O5 content in the range of from 30 to 75% is used.
8. A process as claimed in claim 7 in which phosphoric acid with a P2O5 content greater than 54% and below 75% is used.
9. A process as claimed in claim 1 or 7 in which a solution of the product obtained is subjected to ammoniation to provide a stable solution.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA206,056A CA1078582A (en) | 1974-07-31 | 1974-07-31 | Potassium phosphate fertilisers |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA206,056A CA1078582A (en) | 1974-07-31 | 1974-07-31 | Potassium phosphate fertilisers |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1078582A true CA1078582A (en) | 1980-06-03 |
Family
ID=4100808
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA206,056A Expired CA1078582A (en) | 1974-07-31 | 1974-07-31 | Potassium phosphate fertilisers |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1078582A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112607717A (en) * | 2020-12-18 | 2021-04-06 | 胡渝涛 | Preparation method and application of potassium acid phosphate |
-
1974
- 1974-07-31 CA CA206,056A patent/CA1078582A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112607717A (en) * | 2020-12-18 | 2021-04-06 | 胡渝涛 | Preparation method and application of potassium acid phosphate |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| OA12958A (en) | A process for the manufacture of sulphur-containing ammonium. | |
| US3464808A (en) | Manufacture of ammonium polyphosphate from wet process phosphoric acid | |
| US3713802A (en) | Reaction of phosphoric acid, urea, and ammonia | |
| US3171733A (en) | High-analysis ammonium polyphosphate fertilizer | |
| US3653821A (en) | Process for the manufacture of ammonium polyphosphates | |
| US3920796A (en) | Method of preparing purified phosphates from impure phosphoric acid | |
| US3347656A (en) | Production of potassium ammonium polyphosphate solution | |
| US3554729A (en) | Manufacture of low chloride potassium phosphate fertilizer | |
| US5114460A (en) | Production of low-chloride alkali metal phosphates | |
| CA1078582A (en) | Potassium phosphate fertilisers | |
| US3241946A (en) | Ammonium phosphate fertilizer solids derived from anhydrous liquid phosphoric acid | |
| US3264085A (en) | High analysis ammonium pyrophosphate process and product | |
| US3540874A (en) | Process for the production of ammonium polyphosphate | |
| US3537814A (en) | Ammonium polyphosphate produced at atmospheric pressure | |
| US3243279A (en) | Ammonium phosphate solids derived from anhydrous liquid phosphoric acid | |
| US3533737A (en) | Ammonium polyphosphate produced at atmospheric pressure | |
| US4154800A (en) | Process of producing phosphates and phosphoric acid | |
| US4167406A (en) | High temperature decomposition process for producing an alkali-containing calcined phosphate fertilizer | |
| US3912802A (en) | Ammonium polyphosphates | |
| Madorsky et al. | Potassium Metaphosphate A Potential High-Analysis Fertilizer Material | |
| US2945754A (en) | Granular fertilizer from calcium metaphosphate | |
| US4137063A (en) | Production of potassium polyphosphates from potassium silicofluorides | |
| US3687618A (en) | Recovery of ammonia from exit gases of an ammonium polyphosphate plant | |
| US3228752A (en) | High-analysis ammonium polyphosphate fertilizer | |
| US4017589A (en) | Production of ammonium polyphosphates from melamine phosphates |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |